Pusher furnace

ABSTRACT

An elongated furnace for heat treatment of metallic workpieces which are pushed through the heated furnace chamber along guide means extending from an inlet at one end of the furnace chamber to an outlet at the other end thereof. The elongated guide means comprise metallic elements supported on and in direct contact with water-cooled pipes extending upwardly spaced from the bottom wall of the furnace from the inlet towards the outlet, and a ceramic hearth portion in the region of the outlet and having an upper guide face flush with upper faces of said metallic elements.

United States Patent [191 Herr [ Apr. 16, 1974 PUSHER FURNACE [75]lnventor: Guenter Herr, Oberhausen, Germany [73] Assignee:'Koppers-Wistra-Offenbau GmbH,

Dusseldorf, Germany 22 Filed: Mar. 12,1973

21 Appl.No.:.340,006

[30] Foreign Application Priority Data Sept. 23, 1972 Germany 2246772[52] US. Cl....., 432/234,;432/128 [51] Int. Cl. F27b.9/14 [58] Field ofSearch 432/126-128, 432/233, 234, 227,230, 31, 207, 235

[5 6 I References Cited UNITED STATES PATENTS 3,637,198 1/19 72 Knaak432/234 3,214,152 10/1965 Molz 432/235 3,081,073 3/1963 Conway 432/128FOREIGN PATENTS OR APPLICATIONS 785,960

11/1957 Great Britain 432/233 Primary Examiner-John J. Camby AssistantExaminer-Henry C. Yuen Attorney, Agent, or Firme-Michael S. Striker [57]ABSTRACT An elongated furnace for heat treatment of metallic workpieceswhich are pushed through the heated furnace chamber along guide meansextending from an inlet at one end of the furnace chamber to an outletat the other end thereof. The elongated guide means comprise metallicelements supported on and in direct contactwith water-cooled pipesextending upwardly spaced from the bottom wall of the furnace from theinlet towards the outlet, anda ceramic hearth portion in the region ofthe outlet and having an upper guide face flush with upper faces of saidmetallic elements.

10 Claims, Drawing Figures PUSHER FURNACE BACKGROUND OF THE INVENTIONThe present invention relates to elongated furnaces for heat treatmentof metallic workpieces such as metal blocks, slabs or the like-in whichthe metallic worpieces are pushed in longitudinal direction through thefurnace on guide rails mounted on metal pipes through which coolingwater is circulated and in which the metallic workpieces, while beingpushed along these guide rails, are heated from above and below.

Guide rail constructions for furnaces of the mentioned type are know invarious construction forms. Thus, it has already been suggested toconstruct the guide rails at the inlet end of the furnace chamber asmetallic wear strips which are welded onto upper portions of pipesthrough which cooling water is circulated, whereas in an intermediateregion of the furnace the guide rails are constructed from metallicglide members which are without heat insulation loosely set onto thepipesand removably held thereon. In the region of the outlet ends ofthis known furnace, the guide rails are formed from metallic elementswith pressureresistant heat-insulatin'g members sandwiched between themetallic elements and the water-cooled pipes, and in which the.heat-insulating' members and the heatresistant metallic'members are heldon the pipes by metallic frames welded to the pipes.

Pusher furnaces with guide rail means of the abovementioned type havegiven satisfactory results especially with regard to the requireduniform heating of the workpieces at very high temperatures. In certaincases, however, the use of the insolated'metallic guide members at thelast part of the guidev rails means is not possible .or desirable forconstructive or operative reasons. This is, for instance, the case whenthe pusher furnace has also a lateral discharge opening forpushing theheated workpieces in a direction transverse to the longitudinal axis ofthe guide rail means out of the furnace. Evidently, in this case, thedanger exists that the metallic elements, which are supported by meansof heat-insulating. members on the water-cooled pipes,

.may be damagedor even pushed off the water-cooled SUMMARY OF THEINVENTION It is an object of the present invention to provide anelongated pusher furnace for heat treatment of metallic workpieces inwhich the workpieces may be heated to a uniform temperature throughout.

It is an additional object of the present invention to provide a furnaceof the aforementioned kind which is simple in construction so as tobe'producable at reason-v able cost and soas to stand up under extendeduse, even if the workpieces are pushed out of the furnace in a directiontransverse to the elongation of the latter.

. It is a further object of the invention to provide a furnace of theaforementioned kind which avoids the necessity of heat-insulatedmetallic guide elements at the outlet end of the furnace.

With these and other objects in view, which will become apparent as thedescription proceeds, the pusher furnace according to the presentinvention has an elongated furnace chamber comprising a first zoneadjacent the furnace inlet, a second zone adjacent the furnace outletand an intermediate zone between the first and the second zones.Elongated guide means extend longitudinally through the furnace andcomprise elongated metallic water-cooled guide means extendinglongitudihearth portion in said second zone forming an upper I guideface flush with the upper faces of the metallic guide means. Heatingmeans are provided in the furnace for heating the furnace chamber andthe metallic workpieces pushedthereto.-

The elongated metallic guide means preferably comprise at'least twotransversely spaced metal pipes extending longitudinally through thefirst and intermediate zones for circulation of cooling watertherethrough, and'a metallic wearv strip is welded in the first zone toan upper portion of each pipe, wihereasa plurality of metallic slidemembers are mounted inflthe intermediate zoneof each of the pipes, whilemeans for maintaining the slide member indirect contact with an upperportion of the respective pipe are provided to hold the slide members incontactwith respectivepipe removable therefrom. The heating meanscomprise burner means arranged for heating the' metallic workpieces fromabove and below while the latter are pushed along the metallic guidemeans and the burners are prefera bly arranged in such a manner so as toheat the workpieces as they are pushed along the guide means to a higherdegree in the intermediate zones than in the first and the second zone.

The wear strips are preferably formed from chrome second zone permittingthe workpieces to be pushed out of the furnace chamber in a directiontransverse to the longitudinal direction thereof and this second outletis preferably arranged in the furnace wall which is located laterally ofthe ceramic hearth portion.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional advantages and objects thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal sectionthrough the furnace according to the present invention;

FIG. 2 is a partial transverse cross section taken along the line [I -IIof FIG. 1, drawn to an enlarged scale; and I FIG. 3 is a partialtransverse cross section taken along the line Ill-Ill of FIG. 1,likewise drawn to an enlarged scale.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 schematically illustratesin longitudinal cross section an elongated furnace 1, the walls of whichdefine an elongated furnace chamber having an inlet la at the right end,as viewed in FIG. 1, and an outlet 1b at the left end. The interior ofthe furnace chamber may be considered as divided into three zones, thatis a first zone in the region of the inlet la where the top wall of thefurnace is slightly lower than in the remainder of the furnace, a secondzone in the region of the outlet, that is towards the left of thedownward depression in the top wall of the furnace, and an intermediatezone between the first and the second zone. Elongated guide means extendin longitudinal direction through the furnace chamber from the inlet lato the outlet lb along which metallic workpieces, not shown in thedrawings, are to be pushed through the furnace in the directionindicated by the arrow A. The elongated guide means comprise in thefirst and the intermediate zone at least two transversely spaced metalpipes S,

only the front one is shown in FIG. 1, through which cooling water froma source not shown in the drawing may be circulated. Inthe first'zone aplurality of wear strips 11, as clearlyshown on an enlarged scale inFIG. 2, are welded to the upper portion of the cooling pipe 5 and thesewear strips which may have preferably a square or rectangular crosssection have an upper surface along which the metallic workpieces to betreated in the furnace are. pushed. In the intermediate zone a pluralityof slide members 13 of a height greater than those of the wear stripsare placed on the upper portions of the pipes 5 with the lower ends ofthe slide members 13 have to be flush, that is in one plane with theupper surfaces .of the wear strips 11. Since the slide members 13 arehigher than the wear strips 11, the cross section of the pipes on whichthe slide members are removably supported is preferably reduced ascompared to the cross section of the pipe portions which support thewear strips, as clearly shown in the figures of the drawing. The pipes 5are supported spaced from the bottom wall of the furnace onlongitudinally displaced frame members comprising upright pipes 7 andtransversely arranged pipes 9. In the second zone, that is in the zoneadjacent to the outlet 1b, the guide means comprise a ceramic hearthportion 17 having an upper face flush with the upper faces of the slidemember 13 and the wear strips 11.

The interior of the furnace chamber is heated by a plurality'of burners3, only schematically indicated in FIG. 1 by the center lines of theburners, and it will be seen that the burners are arranged in such amanner that workpieces, when pushed in longitudinal direction throughthe furnace, are heated to a higher degree in the intermediate zone thanin the first and second zones. The height of the slide members 13 ischosen in such a mannner that the cooling of the slide members 13 by thewater circulating through the pipes 5, even at the highest temperaturesand the most unfavorable operating conditions, is great enough that thehottest portions of the slide members 13 will assume only a temperaturein which the material from which the slide members 13 are formed willstill have sufficient rigidity and load-bearing capacity.

The slide members 13 are preferably formed from high heat-resistantsteel, for instance a cobalt steel alloy containing up to about 50percent cobalt, whereas the wear strips 11 may be formed fromchrome-nickel alloy steel.

When metallic workpieces to be heat treated in the furnace chamber arepushed in the direction of the arrow A therethrough, the bottom faces ofthese workpieces will be cooled along portions thereof in contact withthe wear strips 11 or the slide members 13, so that these portions ofthe metallic workpieces will have a temperature smaller than theremainder thereof. To assure a uniform heat distribution throughout thewhole workpieces, which is necessary for the further treatment of suchworkpieces, for instance during rolling of the same, the ceramic hearthportion 17 is provided in the second zone in which a temperatureequalization throughout the workpieces will take place.

The furnace is preferably provided adjacent itsleft end, as viewed inFIG. 1, with a lateral opening 19 in the side wall of the furnacethrough which the heated workpieces may be pushed out of the furnace bya device not shown in the drawing.

The pusher furnace according to the present invention may besuccessfully used in all cases in which the above-described constructionand operating conditions are present. The construction may also be usedwhen existing furnaces, which have already a ceramic hearth portion atthe outlet end, are to be rebuilt, while maintaining the ceramic hearthportion. I v i It will be understood that each of the elements describedabove, or two or more together, may also find a useful application inother types of pusher furnaces differing from the type described above.

While the invention has been illustrated and described as embodied in anelongated pusher furnace having a ceramic hearth portion at the outletend of the furnace and elongated metallic water-cooled guide meansextending longigudinally through the furnace from the inlet end to theceramic. hearth portion, it is not intended to be limited to the detailsshown, since various modifications and structural changes may be madewithout departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

1. A pusher furnace for heat treatment of metallic workpieces, saidfurnace having wall means including a bottom wall defining an elongatedfurnace chamber having an inlet at one end of said elongated furnacechamber and an outlet at the other end thereof, said furnace chambercomprising a first zone adjacent said inlet, a second zone adjacent saidoutlet and an intermediate zone between said first and said secondzones; elongated guide means extending longitudinally through saidfurnace and comprising elongated metallic watercooled guide meansextending only through said first and said intermediate zones spacedfrom said bottom wall and having upper faces along which metallicworkpieces are to be pushed from said inlet towards said outlet, and aceramic hearth portion in said second zone having an upper ceramic guideface flush with said upper faces of said metallic guide means; andheating means in said furnace for heating said furnace chamber andmetallic workpieces pushed therethrough.

2; A furnace as defined inclaim 1, wherein said elongated metallic guidemeans comprise at least two transversely spaced metal pipes extendinglongitudinally through said first and said intermediate zones andarranged for circulation of cooling water therethrough, metallic wearstrips welded in said first zone to an upper portion of each pipe and. aplurality of metallic slide membersmounted in said intermediate zone oneach of said pipes, and means for main-taining said slide members indirect contact with an upper portion of the respective pipe.

3. A furnace as defined in claim 2, wherein said means for maintainingsaid slide members in direct contact with saidpipes comprisemetallicribs welded to said pipes and projecting upwardly therefrom to oppositesides of of said slide members.

4. A furnace as defined in claim 2, and including support meanssupporting said pipes upwardly spaced from said bottom wall.

5. A furnace as defined in claim 4, wherein said heating means comprisesburner means arranged for heating metallic workpieces pushed along saidmetallic guide means from above and below.

6. A furnace as defined in claim 2, wherein said wear strips are formedfrom a chrome-nickelalloy steel and said slide members from a highheat-resistant steel.

7. A furnace as defined in claim 6, wherein said slide members areformed from a cobalt steel alloy containing up to 50 percent cobalt.

8. A furnace as defined in claim 7, wherein said burn-,

ers are arranged to heat workpieces as they are pushed along said guidemeans to a higher degree in said intermediate zone than in said firstand said second zones.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,804,584 Dated April 16 1974 Gue Inventoflg N ter H It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

On the cover sheet, item 175] "Guenter Herr" should read -Guenter HeppSigned and sealed this 1st day of October 1974.

(SEAL) Attest: I

MCCOY 1M. GIBSON JR. 0. MARSHALL DANN Attesting Officer Commissioner ofPatents FORM F o-1050 (10-69) USCOMM'DC cove-ps9 U.S, GOVERNMENT HUNTINGOFFICE: 9 9 0

1. A pusher furnace for heat treatment of metallic workpieces, saidfurnace having wall means including a bottom wall defining an elongatedfurnace chamber having an inlet at one end of said elongated furnacechamber and an outlet at the other end thereof, said furnace chambercomprising a first zone adjacent said inlet, a second zone adjacent saidoutlet and an intermediate zone between said first and said secondzones; elongated guide means extending longitudinally through saidfurnace and comprising elongated metallic watercooled guide meansextending only through said first and said intermediate zones spacedfrom said bottom wall and having upper faces along which metallicworkpieces are to be pushed from said inlet towards said outlet, and aceramic hearth portion in said second zone having an upper ceramic guideface flush with said upper faces of said metallic guide means; andheating means in said furnace for heating said furnace chamber andmetallic workpieces pushed therethrough.
 2. A furnace as defined inclaim 1, wherein said elongated metallic guide means comprise at leasttwo transversely spaced metal pipes extending longitudinally throughsaid first and said intermediate zones and arranged for circulation ofcooling water therethrough, metallic wear strips welded in said firstzone to an upper portion of each pipe and a plurality of metallic slidemembers mounted in said intermediate zone on each of said pipes, andmeans for main-taining said slide members In direct contact with anupper portion of the respective pipe.
 3. A furnace as defined in claim2, wherein said means for maintaining said slide members in directcontact with said pipes comprise metallic ribs welded to said pipes andprojecting upwardly therefrom to opposite sides of of said slidemembers.
 4. A furnace as defined in claim 2, and including support meanssupporting said pipes upwardly spaced from said bottom wall.
 5. Afurnace as defined in claim 4, wherein said heating means comprisesburner means arranged for heating metallic workpieces pushed along saidmetallic guide means from above and below.
 6. A furnace as defined inclaim 2, wherein said wear strips are formed from a chrome-nickel alloysteel and said slide members from a high heat-resistant steel.
 7. Afurnace as defined in claim 6, wherein said slide members are formedfrom a cobalt steel alloy containing up to 50 percent cobalt.
 8. Afurnace as defined in claim 7, wherein said burners are arranged to heatworkpieces as they are pushed along said guide means to a higher degreein said intermediate zone than in said first and said second zones.
 9. Afurnace as defined in claim 1, and including a second outlet in saidsecond zone permitting the workpieces to be pushed out of said furnacechamber in a direction transverse to the longitudinal direction thereof,said second outlet being arranged in a portion of said wall means whichis located laterally of said ceramic hearth portion.
 10. A furnace asdefined in claim 5, wherein said burner means are arranged for heatingmetallic workpieces pushed along said ceramic hearth portion only fromabove.